Atlantic Tropical Weather Discussion (Text)

000
AXNT20 KNHC 092320
TWDAT
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
619 PM EST FRI DEC 9 2016
Tropical Weather Discussion for North America, Central America
Gulf of Mexico, Caribbean Sea, northern sections of South
America, and Atlantic Ocean to the African coast from the
Equator to 32N. The following information is based on satellite
imagery, weather observations, radar and meteorological analysis.
Based on 1800 UTC surface analysis and satellite imagery through
2300 UTC.
...SPECIAL FEATURES...
...Gulf of Mexico Gale Warning...
A strong high pressure ridge has built across the north and
western Gulf of Mexico today, and southward across eastern
Mexico, behind a cold front that currently extends from the
northwest coast of Cuba to 22N93.5W to 18N92.5W. A very strong
pressure gradient between the ridge and the front is producing a
large area of minimal to strong gale force winds this afternoon.
Afternoon ASCAT data indicated 25-35 kt N to NE winds across much
of the NW Gulf, and NW winds of 35-45 kt across the SW Gulf west
of the front. This is generating a large area of high seas 12 to
20 ft NW of the front. a 1039 mb high pressure center across
northern Arkansas anchors the ridge, and is forecast to shift
eastward during the next 24 hours. As this occurs the front will
sink slightly southward, and the pressure gradient will gradually
decrease across the NW Gulf. However, gale force NW winds are
expected to continue through Saturday evening offshore of
Veracruz, Mexico. Please read the High Seas Forecast product
under AWIPS/WMO headers MIAHSFAT2/FZNT02 KNHC for more details.
...ITCZ/MONSOON TROUGH...
The Monsoon Trough extends across the African Continent reaching
the Atlantic Ocean near 06N12W. The ITCZ continues from that
point to 04.5N20W to 05.5N40W. A low latitude easterly wave, with
a north to south aligned trough at the surface, is along 39W and
southward of 10N. Active convection continues along the ITCZ,
where scattered moderate to strong is observed from 03N-09N
between 16W and 40W.
...DISCUSSION...
GULF OF MEXICO...
1600 UTC ASCAT scatterometer data depicts gale force winds
occurring over much of the western Gulf west of 90W, while strong
NW gales to 45 kt prevail south of 22N and west of the front.
Please refer to the section above for details. A cold front has
moved southward across the Straits of Florida and extends from NW
Cuba to 22.5N88W, then is stationary to 22N93.5W, then continues
across the Mexican coast near 18.5N93.5W. Broken multi- layered
cloudiness and isolated moderate convection is observed along and
north of the front some 240 nm, with scattered moderate to strong
convection along the stationary portion of the front. Fresh to
strong north-northeast winds prevail across the eastern Gulf
waters. The front is expected to meander across the southern
Straits of Florida and northwest Cuba this weekend with northerly
winds slowly diminishing below gale force late Sat in the western
Gulf.
CARIBBEAN SEA...
A broad upper ridge generally prevail over the basin, while a TUTT
low in the middle to upper levels near 15N76W continues to move
westward across the central Caribbean. This TUTT low has been
moving W and in synch with an easterly wave currently along 73W.
Anticyclonic diffluent upper level flow to the east of the TUTT
low is providing a favorable environment for persistent convection
along and east of the easterly wave. Fresh to locally strong NE to
E winds are occurring north of 14N both east and west of the wave
axis and have built seas to 6-9 ft there. The wave will continue
west across the basin and enter Central America early Sun.
Elsewhere at the surface, the Monsoon Trough extends along 10N
with scattered moderate convection between 78W-85W. Outside of the
easterly wave, moderate to fresh NE trades prevail across the
remainder of the basin, except fresh NE winds in the Yucatan
Channel near the approaching cold front. Fresh to occasional
strong trades are expected across the south-central Caribbean
mainly north of Colombia tonight through late Saturday with
trades increasing slightly through the remainder of the weekend as
the strong ridge affecting the Gulf of Mexico shifts eastward into
the western Atlantic. The cold front will meander across the
Yucatan Channel, with associated conditions across the Gulf
spreading modestly into NW portions.
...HISPANIOLA...
Fair weather prevails across the island at this time as subsidence
and dry air ahead of the easterly wave along 73W have dominated
the island today. A modest increase in low level moisture will
spread westward across the area this evening and tonight and
should lead to passing tradewind showers across the area.
Generally fair conditions are expected through the weekend.
ATLANTIC OCEAN...
A cold front extends across the western Atlantic from 31N67W
through the NW Bahamas to northwestern Cuba. Broken multi-
layered cloudiness and isolated convection is observed along and
northwest of the front. A weak and narrow surface ridge is SE of
the front and extends across the remainder of the basin, anchored
on a 1020 mb surface high centered near 23N54W. A pair of
weakening frontal boundaries were analyzed north of the ridge. The
first is a dissipating stationary front from 27N72W to 28N58W to
27N48W to a 1017 mb surface low near 32N39W. The next dissipating
cold front extends from 31N22W to 26N31W. No significant
convection is related to any of these fronts. Expect the cold
front in the west Atlantic to continue moving east of the Bahamas
while it drifts slightly Se across the Bahamas. As mentioned
above, as the surface ridge behind this cold front begins to shift
eastward into the Atlantic tonight and Sat, look for increasing Ne
winds and building seas behind the cold front. Little change is
expected elsewhere.
For additional information please visit
http://www.hurricanes.gov/marine
$$
Stripling